CrossShade allows the creation of 3D-looking shaded
production drawings from concept sketches. We use
artist-drawn cross-section lines to automatically infer
surface information across the sketch, enabling 3D-like
rendering.

Cross-sections function as an aid to both sketch creation
and viewer understanding of the depicted 3D shape. In
particular, intersections of these curves, or cross-hairs,
convey valuable 3D information that viewers compose into a
mental model of the sketch. We use this
information to estimate the surface normals.

Combined with conventional shaders, our normals
facilitate the creation of shaded drawings as in the
gallery below.